1. Field of the Invention
The invention relates to components for forming ferrite elements and, more particularly, for forming a ferrite bobbin.
2. Background of the Invention
Ferrite bobbins are known in the prior art. The bobbins are generally spool shaped with two enlarged flange portions and a shaft extending between the flange portions about which an electric conductor is wound. Referring to FIGS. 1(a)-(c), a multi-component prior art ferrite bobbin 1 is shown therein. Specifically, the ferrite bobbin shown is Part No. 9677182209 manufactured by Fair-Rite Products Corporation, Walkill, N.Y., the assignee herein. As shown in FIG. 1, the ferrite bobbin 1 is formed from three separate components, namely, disc-shaped flanges 2, 3 and a shaft 4. In forming the ferrite bobbin 1, each individual component is separately prepared from ferrite, and then, assembled using glue. This design, although very simple, suffers from some drawbacks. First, as can be readily appreciated, attention must be paid to ensure the flanges 2 and 3, and the shaft 4 are in proper axial alignment during assembly. Also, as shown in FIG. 1(b), each of the flanges 2, 3 is formed with a pair of diametrically-opposed slots S. The slots S are used in facilitating winding of a wire about the ferrite bobbin 1, as well as, providing spaces for engaging support pins or locator pins on a circuit board. It is desired that the slots of both the flanges 2 and 3 be axially aligned to allow for proper cooperation with any pins. The flange portions 2, 3 however do not have an arrangement to ensure axial alignment and components are occasionally formed with the slots S being out of axial alignment.
In FIG. 2, Part No. 9677142009 sold by Fair-Rite Products Corporation is shown, which is representative of a second type of ferrite bobbin design. Referring to FIG. 2, a ferrite bobbin 5 is depicted which is unitarily formed from a single piece of ferrite material and shaped to define two enlarged flange portions 6, 7 and a central shaft 8. To prepare the ferrite bobbin 5, a slug of ferrite material is first formed which defines the same outer dimensions of the ferrite bobbin 5. By example, to form the ferrite bobbin 5, a slug would have to be provided having a rectangular profile with a width "W" extending between the outer faces 9, 10 of the flange portions 6 and 7, and a height D.sub.2, as shown in dashed lines. The slug is then machined, e.g. by centerless plunge grinding, to form the shape of the ferrite bobbin 5 with the central shaft 8 having a reduced diameter D.sub.2. As with all prior art ferrite bobbin designs, the flange portions 6, 7 and the central shaft 8 can be formed with circular shapes, as shown, or alternatively with various polygonal shapes. Although this second type of prior art design does not require any assembly, this design suffers from some drawbacks. First, the step of machining and the material waste produced by machining are undesired. Also, the machining process causes the flange portions 6 and 7 to each have a sharp inner edge 11. As a result, during the process of winding a wire on the ferrite bobbin 5, care must be exercised to ensure that the wire does not overly rub against the edges 11, resulting in the wire being cut, frayed or damaged in any other way. To avoid this problem, the edges 11 can be "broken" with a rounded or beveled shape, but to achieve this result, an additional manufacturing step is required in forming the ferrite bobbin 5.
It should be noted that a unitary ferrite bobbin cannot be readily formed directly from ferrite material. In particular, the process of forming a ferrite component such as a slug, disc, bead, and so on typically involves press compaction molding of ferrite material into the desired form. The shape of an entire bobbin, as shown in FIG. 1(a) and FIG. 2, cannot be press compaction molded. It should also be noted, entire ferrite bobbins have been unitarily manufactured from an injection molding process. However, injection molding requires the inclusion of a binder material in the ferrite prior to molding. With current binders, time consuming procedures are required to remove the binder from the molded ferrite component (e.g. submersion of the components in a chemical bath for a period of time). As is readily appreciated, the increase in size of injection-molded ferrite components results in an increase in the period of time and the amount of effort to be exerted required for binder-material removal. Thus, the process of injection molding ferrite bobbins has commercial and practical limitations, especially with respect to larger size ferrite bobbin components.
It is an object of the subject invention to provide components for easily and efficiently forming a ferrite bobbin.